1. Technical Field of the Invention
The invention relates to an operation panel arranged outside an electronic device and used for various input operations and also to provide an electronic device provided with such an operation panel.
2. Description of Related Arts
An electronic device in an image forming apparatus or the like is typically loaded with an operation panel including operation keys for input operations and a display section for displaying a working state of the apparatus. FIG. 6 is an external perspective view of a conventional operation panel. FIG. 7 is an exploded perspective view of the conventional operation panel as viewed from the rear side thereof. FIG. 8 is an enlarged view of an operation key portion of the conventional operation panel. The operation panel 1 has a control board, not shown, arranged inside an operation section cover 2, on the front surface of which a plurality of operation keys 3 for inputting various commands to the control board and a display section 5 for displaying a working state of the apparatus are provided.
The operation key 3 has a flange section 3a formed larger than a guide hole 4 and an operation section 3b projecting toward the front side of the operation section cover 2 via the guide hole 4. On the rear surface of the flange section 3a, a connecting terminal 6 is provided. The user can press the operation section 3b to thereby bring it into contact with a contact on the control board or separate therefrom. In each of the flange section 3a, two boss holes 8 are formed which respectively fit with bosses 7 formed on the rear surface of the operation section cover 2.
In such an operation panel 1, a small difference between the inner dimension of the guide hole 4 and the outer dimension of the operation key 3 has created, for example, a problem that pressing an edge of the operation key 3 or pressing the operation key 3 diagonally by the user causes interference between the operation key 3 and the edge of the guide hole 4, bringing the operation key 3 into a nonoperational state (locked state). Thus, a method of providing a relatively large difference between the inner dimension of the guide hole 4 and the outer dimension of the operation key 3 to avoid the locking of the operation key 3 has been adopted. However, this method encounters a problem that shift of the operation key 3 from the center of the guide hole 4 leaves an outstanding clearance between the operation key 3 and the guide hole 4, thus deteriorating the appearance of the device.
In recent years, especially adoption of universal design that can be used regardless of age and sex, presence or absence of disability, and individual capabilities has increased the number of electronic devices whose operability is enhanced by tilting an entire operation panel. In the operation panel 1 loaded in such an electronic device, the operation key 3 moves to the lower end of the guide hole 4 by its own weight, and as shown in FIG. 8, a clearance 9a between the operation key 3 and the upper end of the guide hole 4 is wider than a clearance 9b between the operation key 3 and the lower end of the guide hole 4.
As a method of fitting an operation key to an operation section cover, Patent document 1 discloses, for example, an operation panel in which a clearance between an operation button and a frame holding the operation button is provided and the operation button is positioned by a hole formed in an external cover fixed on the frame. Patent document 2 discloses an operation button holding mechanism including an elastic member biasing a flange section of a first operation button and an elastic sheet formed into a thin plate extending from the elastic member, in which mechanism supporting can be achieved by biasing second operation buttons having flange sections of different thicknesses.
However, the method of patent document 1 performs positioning of the operation button with the external cover hole. Thus, this method requires a small difference between the inner dimension of the external cover hole and the outer dimension of the operation button, thus causing a risk of interference and thus locking between the external cover and the operation button. Moreover, the method of patent document 2 makes it easy to perform positioning in the operation direction of the operation button, that is, the direction vertical to the operation surface. However, the method of patent document 2 does not consider positioning in the direction horizontal to the operation surface, thus resulting in failure to prevent locking of the operation button and deterioration in design caused by displacement of the operation button.    [Patent Document 1] JP-A-H11-306903    [Patent Document 2] JP-A-2000-276963